Chimeric gene with several herbicide tolerance genes, plant cell and plant resistant to several herbicides

ABSTRACT

1. Chimeric gene containing several herbicide tolerance genes, plant cell and plant which are tolerant to several herbicides. 
     2. The plant is tolerant to several herbicides at the same time, in particular to the inhibitors of HPPD and to those of EPSPS and/or to the dihalohydroxybenzonitriles. 
     3. Use for removing weeds from plants with several herbicides.

The subject of the present invention is a chimeric gene containingseveral herbicide tolerance genes, a plant cell and a plant which aretolerant to several herbicides.

In the remainder of the description, herbicides will be designated bythe common name in particular referenced in “The Pesticide Manual” 10thedition by British Crop Protection Council.

Plants are known which have been transformed so as to be tolerant tocertain herbicides such as especially dihalohydroxybenzonitriles, inparticular bromoxynil and ioxynil, by means of the gene encoding thenitrilase degrading these herbicides or those tolerant to theEPSPS-inhibiting herbicides, in particular glyphosate, sulfosate orfosametin or tolerant to the acetolactatesynthase (ALS) inhibitors ofthe sulphonylurea type or to the dihydropteroate synthase inhibitorssuch as asulam or to the glutamine synthase inhibitors such asglufosinate.

Some herbicides are known, such as the isoxazoles described especiallyin French Patent Applications 95 06800 and 95 13570 and in particularisoxaflutole, a herbicide which is selective for maize, thediketonitriles such as those described in European Applications 0 496630, 0 496 631, in particular 2-cyano-3-cyclopropyl-1-(2-SO₂CH₃-4-CF₃phenyl)propane-1,3-dione and 2-cyano-3-cyclopropyl-1-(2-SO₂CH₃-4-2,3Cl₂phenyl)propane-1,3-dione, the triketones described in EuropeanApplications 0 625 505 and 0 625 508, in particular sulcotrione or thosedescribed in U.S. Pat. No. 5,506,195, or the pyrazolinates. Furthermore,the gene encoding the HPPD conferring tolerance to the latter herbicideshas been isolated and transgenic plants containing it have been obtainedshowing a significant tolerance and are the subject of unpublishedFrench Applications No. 95/06800, 95/13570 and 96/05944.

However, agricultural practice shows that farmers like to have, fortreating plants and in particular crops, combinations of herbicides, inparticular to respond to the various problems of weed removal due to thelimits of the herbicide spectrum taken separately. It may be, inaddition, advantageous to have a selectable marker gene combined with aherbicide tolerance gene. A need therefore exists for plants and inparticular for crops exhibiting tolerance to several herbicides,preferably at least two or three.

It has now been discovered that it is possible to confer multipleherbicide tolerance on a plant cell and on a plant.

The subject of the present invention is first a chimeric gene comprisingat least two basic chimeric genes each containing, in the direction oftranscription, regulatory elements necessary for its transcription inplants, that is to say at least one regulatory promoter sequence, atleast one heterologous coding part comprising a coding sequence encodingan enzyme conferring on plants the tolerance to a herbicide and at leastone regulatory terminator sequence or one polyadenylation sequence.

As coding sequence, there may be used in particular all those known toconfer on plants tolerance to certain inhibitors such as:

-   that for EPSPS for tolerance to glyphosate, to sulfosate or to    fosametin, in particular those for the mutated or nonmutated    protein, there may be mentioned in particular patents:    -   U.S. Pat. No. 4,535,060, EP 115 673, U.S. Pat. No. 4,796,061,        U.S. Pat. No. 5,094,945; U.S. Pat. No. 4,971,908, U.S. Pat. No.        5,145,783, EP 293 358; EP 378 985, WO 91/04323; WO 92 044 449;        WO 92 06201. In the text which follows, this type of gene will        be designated by the sequence or gene “EPSPS”.

There may also be mentioned glyphosate oxydoreductase (cf. WO 92/000377), an enzyme for the detoxification of glyphosate.

-   -   that of the gene for the Klebsiella sp. nitrilase for tolerance        to the dihalobenzonitriles which is described in U.S. Pat. No.        4,810,648 and in particular the gene derived from Klebsiella        ozaenae, which will be designated in the text which follows by        “OXY” gene or sequence,    -   that for HPPD as described in unpublished French Publications        No. 95/06800, 95/13570 and 96/05944 which are cited above. This        HPPD may be of any type.

More particularly, this sequence may be of bacterial origin, such as inparticular the genus Pseudomonas or of plant origin, such as inparticular a monocotyledonous or dicotyledonous plant, in particularArabidopsis or umbelliferous plants such as for example carrots (Daucuscarota). It may be a native or a wild-type sequence or possibly mutatedwhile fundamentally retaining a property of herbicide tolerance to HPPDinhibitors, such as the herbicides of the family of isoxazoles or ofthat of the triketones or the pyrazolinates.

Other sequences may be used:

-   -   that for phosphinotricyine acetyl transferase or that for        glutamine synthase for tolerance to glufosinate (cf. EP 0 242        236)    -   that for dihydropteroate synthase for tolerance to asulam (cf.        EP 0 369 367)    -   that for ALS for tolerance to sulphonylureas    -   that for protoporphyrogen oxidase (“protox”) for tolerance to        herbicides of the family of diphenyl ethers such as acifluorfen        or oxyfluorfen or that for the oxadiazoles such as oxadiazon or        oxadiargyl and that for the cyclic imides such as chlorophthalim        or that for the phenylpyrrazoles such as TNP or that for the        pyridines and the phenopylates and carbamate analogues (of. WO        95/34659).

Preferably, one of the chimeric genes contains a coding sequence forHPPD. In this case, the other sequence(s) may be of any type and may bein particular chosen from the abovementioned group. Preferably, theother sequences are chosen from the group comprising the nitrilase genefor tolerance to the dihalohydroxybenzonitriles and an EPSPS gene.

The chimeric genes according to the invention may, in addition, containgenes encoding properties other than of herbicide tolerance such as, forexample, genes for resistance to insects, such as those of the Bacillusthurigensis type conferring resistance to various representatives of thecoleoptera and Lepidoptera family, or genes for resistance to nematodes,genes for resistance to fungal or microbial diseases, or genesconferring agronomic properties such as the genes for the variousdesaturases involved in the production of fatty acids. There may bementioned, in particular, that for the delta-6 desaturase described inInternational Application WO 93/06712.

As regulatory promoter sequence, use may be made of any promotersequence of a gene which is expressed naturally in plants, in particulara promoter of bacterial, viral or plant origin such as, for example,that of a gene for the small subunit of ribulose biscarboxylase(RuBisCO) or that of a gene for α-tubulin (European Application EP No. 0652 286), or of a plant virus gene such as, for example, that from thecauliflower mosaic virus (CaMV 19S or 35S), but any known suitablepromoter may be used. Preferably, use is made of a regulatory promotersequence which promotes the overexpression of the coding sequence, suchas, for example, that comprising at least one histone promoter asdescribed in European Application EP 0 507 698.

According to the invention, it is also possible to use, in combinationwith the regulatory promoter sequence, other regulatory sequences whichare situated between the promoter and the coding sequence, such astranscription activators, “enhancer”, such as for example the tobaccoetch virus (TEV) translation activator described in Application WO87/07644, or transit peptides, either single, or double, and in thiscase optionally separated by an intermediate sequence, that is to saycomprising, in the direction of transcription, a sequence encoding atransit peptide for a plant gene encoding a plastid localization enzyme,a portion of sequence of the N-terminus mature portion of a plant geneencoding a plastid localization enzyme, and then a sequence encoding asecond transit peptide for a plant gene encoding a plastid localizationenzyme, consisting of a portion of sequence of the N-terminus matureportion of a plant gene encoding a plastid localization enzyme, asdescribed in European Application No. 0 508 909.

As regulatory terminator sequence or polyadenylation sequence, use maybe made of any corresponding sequence of bacterial origin, such as forexample the Agrobacterium tumefaciens nos terminator, or of plantorigin, such as for example a histone terminator as described inEuropean Application EP No. 0 633 317.

The subject of the invention is also a plant cell, from monocotyledonousor dicotyledonous plants, especially crops, which is tolerant to atleast two herbicides of which at least one is an HPPD inhibitor. Thiscell may contain at least two chimeric genes each comprising a sequenceencoding tolerance to a herbicide and one of which comprises a sequenceencoding HPPD. The two chimeric genes may be either carried by the samevector, or each on a different vector, or delivered as such byintroducing into the cell by physical or physicochemical means, forexample by microinjecton, electroporation or bombardment, according tomethods known per se.

The subject of the invention is also a transformed plant which istolerant to at least two herbicides, one of which is an HPPD inhibitor.This plant may be obtained either by crossing at least two plants eachcontaining a gene encoding tolerance to a herbicide, or by regenerationof a cell according to the invention, as described above. The plants maybe monocotyledonous or dicotyledonous, especially crops, major cropssuch as for example, but with no limitation being implied, for thedicotyledonous plants, tobacco, cotton, rapeseed, soya and beet, and forthe monocotyledonous plants maize and straw cereals, or market garden orflower crops.

The subject of the invention is also a process for producing plants withmultiple herbicide tolerance by plant transgenesis, characterized inthat:

-   -   in a first stage, there is inserted into several cells        respectively one of the basic genes each containing regulatory        elements necessary for its transcription in plants and a coding        sequence encoding an enzyme conferring on plants tolerance to a        herbicide, and in that    -   the plants are then crossed in order to obtain plants with        multiple tolerance.

The subject of the invention is also another process for producingplants with multiple herbicide tolerance by plant transgenesis, a firststage comprising the integration, into plant cells, of at least twogenes for tolerance to a herbicide of which at least one is an HPPDinhibitor, the second stage comprising the regeneration of the plantfrom the transformed cells according to the invention.

The transformation may be obtained by any appropriate means known,widely described in the specialized literature and in particular thepatents and applications cited in the present application.

One series of methods consists in bombarding cells or protoplasts withparticles to which DNA sequences are attached. According to theinvention, these DNAs may be carried by the same particles or bydifferent bombardments. Another series of methods consists in using, asmeans of transfer into the plant, a chimeric gene inserted into anAgrobacterium rhizogenes Ri or Agrobacterium tumefaciens Ti plasmid.

Other methods may be used, such as microinjection or electroporation.

Persons skilled in the art will choose the appropriate method accordingto the nature of the plant, in particular its monocotyledonous ordicotyledonous character.

It has been observed that transformed plants according to the inventionexhibit significant tolerance to the hydroxyphenyl pyruvate dioxygenaseinhibitors such as some recent herbicides such as the isoxazolesdescribed in particular in French Patent Applications 9 506 800 and 9513570 and in particular4-[4-CF3-2-(methylsulphonyl)benzoyl]-5-cyclopropylisoxazole, or“isoxaflutole”, a herbicide which is selective for maize, thediketonitriles such as those described in European Applications 0 496630, 0 496 631, in particular 2-cyano-3-cyclopropyl-1-(2-SO₂CH₃-4-CF₃phenyl)propane-1,3-dione and 2-cyano-3-cyclopropyl-1-(2-SO₂CH₃-4-2,3 Cl₂phenyl)propane-1,3-dione, the triketones described in EuropeanApplications 0 625 505 and 0 625 508, in particular sulcotrione and thepyrazinolates. These same plants according to the invention exhibitsignificant tolerance to other herbicides such as for example thedihalobenzonitriles, in particular bromoxynil and ioxynil, glyphosateand its analogues, glufosinate.

The subject of the present invention is also the plants regenerated fromtransformed cells. The regeneration is obtained by any appropriateprocess which depends on the nature of the species, as for exampledescribed in the above applications. The plants according to theinvention may also be obtained by crossing parents, each of themcarrying one of the genes for herbicide tolerance described.

The subject of the invention is finally a process for removing weed fromplants, in particular crops, with the aid of a herbicide of this type,characterized in that this herbicide is applied to transformed plantsaccording to the invention, presowing, preemergence and postemergence ofthe crop. Herbicide for the purposes of the present invention isunderstood to mean a herbicidal active substance, alone or combined withan additive which modifies its efficacy, such as for example an agentwhich increases activity (synergist) or which limits activity (safener).

Of course, for their practical application, the above herbicides arecombined, in a manner known per se, with the formulation adjuvantsnormally used in agricultural chemistry.

According to the invention, one of the herbicide tolerance genes presentin the plants may be used as a selectable marker, either in vitro or invivo.

The various aspects of the invention will be understood more clearlywith the aid of the experimental examples below.

EXAMPLE 1 Isolation of the HPPD Gene from P. fluorescens A 32

From the amino acid sequence of HPPD from Pseudomonas sp. P.J. 874(published by Rüetschi U. et al. 1992. Eur. J. Biochem. 205: 459-466),the sequence of the different oligonucleotides is deduced so as toamplify, by PCR, a portion of the coding sequence of HPPD from P.fluorescens A32 (isolated by McKellar, R. C. 1982. J. Appl. Bacteriol.53: 305-316). An amplification fragment of the gene for this HPPD wasused to screen a P. fluorescens A32 partial genomic library and thus toisolate the gene encoding this enzyme.

A) Preparation of the P. fluorescens A32 Genomic DNA.

The bacterium was cultured in 40 ml of M63 minimum medium (KH₂PO₄ 13.6g/l, (NH₄)₂SO₄ 2 g/l, MgSO₄ 0.2 g/l, FeSO₄ 0.005 g/l pH 7 plus 10 mML-tyrosine as sole carbon source) at 28° C. for 48 hours.

After washing, the cells are taken up in 1 ml of lysis buffer (100 mMTris-HCl pH 8.3, 1.4 M NaCl and 10 mM EDTA) and incubated for 10 minutesat 65° C. After treating with phenol/chloroform (24/1) and treating withchloroform, the nucleic acids are precipitated by addition of one volumeof isopropanol and then taken up in 300 μl of sterile water and treatedwith RNAse 10 μg/ml final. The DNA is again treated withphenol/chloroform, chloroform and reprecipitated by addition of a 1/10volume of 3 M sodium acetate pH 5 and 2 volumes of ethanol. The DNA isthen taken up in sterile water and assayed.

B) Choice of the Oligonucleotides and Syntheses

From the amino acid sequence of the HPPD from Pseudomonas sp. P.J. 874,five oligonucleotides are chosen, two are directed in the direction NH₂terminus of the protein towards the COOH terminus of the protein andthree directed in the opposite direction (see FIG. 1). The choice wasdictated by the following two rules:

-   -   a 3′ end of the stable oligonucleotide, that is to say at least        two bases with no ambiguity,    -   a degeneracy as low as possible.

The chosen oligonucleotides have the following sequences:

P1: 5′TA(C/T)GA(G/A)AA(C/T)CCIATGGG3′ P2: 5′GA(G/A)ACIGGICCIATGGA3′P3: 5′AA(C/T)TGCATIA(G/A)(G/A)AA(C/T)TC(C/T)TC3′P4: 5′AAIGCIAC(G/A)TG(C/T)TG(T/G/A)ATICC3′PS: 5′GC(C/T)TT(A/G)AA(A/G)TTICC(C/T)TCICC3′

They were synthesized on the synthesizer “cyclone plus DNA synthesizer”of MILLPORE brand.

With these five oligonucleotides, by PCR, the amplification fragmentswhich should be theoretically obtained according to the sequence SEQ IDNo. 1 have the following sizes:

with the primers P1 and P3

about 690 bp

with the primers P1 and P4

about 720 bp

with the primers P1 and P5

about 1000 bp

with the primers P2 and P3

about 390 bp

with the primers P2 and P4

about 420 bp

with the primers P2 and P5

about 700 bp

C) Amplification of a Coding Portion of the HPPD from P. fluorescens A32

The amplifications were carried out on a PERKIN ELMER 9600 PCR apparatusand with the PERKIN ELMER Taq polymerase with its buffer, under standardconditions, that is to say for 50 μl of reaction, there are the dNTPs at200 μM, the primers at 20 μM, the Taq polymerase 2.5 units and the DNAfrom P. fluorescens A32 2.5 μg.

The amplification programme used is 5 min at 95° C., then 35 cycles <45sec 95° C., 45 sec 49° C., 1 min 72° C.>followed by 5 min at 72° C.

Under these conditions, all the amplification fragments obtained have asize which is compatible with the theoretical sizes given above, whichis a good indication of the specificity of the amplifications.

The amplification fragments obtained with the pairs of primers P1/P4,P1/P5 and P2/P4 are ligated into pBSII SK(−) after digesting thisplasmid with EcoRV and treating with terminal transferase in thepresence of ddTTP as described in HOLTON T. A. and GRAHAM M. W., 1991,N.A.R., Vol. 19, No. 5, p. 1156.

A clone of each of the three types is partially sequenced; this makes itpossible to confirm that in the three cases, part of the coding regionof the HPPD from P. fluorescens A32 has indeed been amplified. The P1/P4fragment is retained as probe in order to screen a P. fluorescens A32partial genomic library and to isolate the complete HPPD gene.

D) Isolation of the Gene

By Southern, it is shown that a 7 Kbp fragment, after digestion of theP. fluorescens A32 DNA with the restriction enzyme BamHI, hybridizeswith the HPPD P1/P4 probe. 400 μg of P. fluorescens A32 DNA weretherefore digested with the restriction enzyme BamHI and the DNAfragments of about 7 Kbp were purified on agarose gel.

These fragments are ligated into pBSII SK(−), itself digested with BamHIand dephosphorylated by treating with alkaline phosphatase. Aftertransformation in E. coli DH10b, the partial genomic library is screenedwith the HPPD P1/P4 probe.

A positive clone was isolated and called pRP A. Its simplified map isgiven in FIG. 2. The position of the coding part of the HPPD gene isindicated on this map. It is composed of 1077 nucleotides which encode358 amino acids (see SEQ ID No. 1). The HPPD from P. fluorescens A32exhibits good amino acid homology with that from Pseudomonas sp. strainP.J. 874; there is indeed 92% identity between these two proteins (seeFIG. 3).

EXAMPLE 2 Construction of Two Chimeric Genes with an HPPD Sequence

To confer on plants tolerance to herbicides which inhibit HPPD, twochimeric genes are constructed:

The first consists in placing the coding part of the HPPD gene from P.fluorescens A32 under the control of the double histone promoter(European Patent Application No. 0 507 698) followed by the tobacco etchvirus translational enhancer (TEV) (pRTL-GUS (Carrington and Freed,1990; J. Virol. 64: 1590-1597)) with the terminator of the nopalinesynthase gene. The HPPD will then be located in the cytoplasm.

The second will be identical to the first, the only difference beingthat between the TEV translation activator and the coding portion ofHPPD, the optimized transit peptide (OTP) is intercalated (EuropeanApplication EP No. 0 508 909). The HPPD will then be located in thechloroplast.

A) Construction of the vector pRPA-RD-153:

-   -   pRPA-RD-11: a derivative of pBS-II SK(−) (Stratagene catalogue        #212206) containing the nopaline synthase polyadenylation site        (NOS polyA) (European Application No. 0 652 286) is cloned        between the KpnI and SalI sites. The KpnI site is converted to        an NotI site by treating with T4 DNA polymerase I in the        presence of 150 μM deoxynucleotide triphosphates, followed by        ligation with an NotI linker (Stratagene catalogue #1029). Thus,        an NOS polyA cloning cassette is obtained.    -   pRPA-RD-127: a derivative of pRPA-BL-466 (European Application        EP No. 0 337 899) cloned into pRPA-RD-11 creating a cassette for        expression of the oxy gene and containing the promoter of the        ribulose biscarboxylase small subunit:

“promoter (SSU)−oxy gene−NOS polyA”

To create this plasmid, pRPA-BL-488 was digested with XbaI and HindIIIin order to isolate a 1.9 kbp fragment containing the SSU promoter andthe oxy gene, which was ligated into the plasmid pRPA-RD-11 digestedwith compatible enzymes.

-   -   pRPA-RD-132: it is a derivative of pRPA-BL-488 (European        Application EP No. 0 507 698) cloned into pRPA-RD-127 with        creation of a cassette for expression of the oxy gene with the        double histone promoter:

“double histone promoter−oxy gene−NOS polyA”

To manufacture this plasmid, pRPA-BL-466 is digested with HindIII,treated with Klenow and then redigested with NcoI. The purified 1.35 kbpfragment containing the double histone promoter H3A748 is ligated withthe plasmid pRPA-RD-127 which had been digested with XbaI, treated withKlenow and redigested with NcoI.

-   -   pRPA-RD-153: it is a derivative of pRPA-RD-132 containing the        tobacco etch virus (TEV) translation activator. pRTL-GUS        (Carrington and Freed. 1990; J. Virol. 64: 1590-1597) is        digested with NcoI and EcoRI and the 150 bp fragment is ligated        into pRPA-RD-132 digested with the same enzymes. An expression        cassette containing the promoter has therefore been created:

“double histone promoter−TEV−oxy u−NOS polyA”

B) Construction of the vector pRPA-RD-185:

pUC19/GECA: a derivative of pUC-19 (Gibco catalogue #15364-011)containing numerous cloning sites. pUC-19 is digested with EcoRI andligated with the oligonucleotide linker 1:

Linker 1: AATTGGGCCA GTCAGGCCGT TTAAACCCTA GGGGGCCCGCCCGGT CAGTCCGGCA AATTTGGGAT CCCCCGGGC TTAA

The clone selected contains an EcoRI site followed by the polylinkerwhich contains the following sites: EcoRI, ApaI, AvrII, PmeI, SfiI,SacI, KpnI, SmaI, BamHI, XbaI, SalI, PstI, SphI and HindIII.

pRPA-RD-185: it is a derivative of pUC19/GECA containing a modifiedpolylinker. pUC19/GECA is digested with HindIII and ligated with thelinker oligonucleotide 2:

Linker 2: AGCTTTTAAT TAAGGCGCGC CCTCGAGCCT GGTTCAGGGAAATTA ATTCCGCGCG GGAGCTCGGA CCAAGTCCC TCGA

The clone selected contains a HindIII site in the middle of thepolylinker which now contains the following sites: EcoRI, ApaI, AvrII,PmeI, SfiI, SacI, KpnI, SmaI, BamHI, XbaI, SalI, PstI, SphI, HindIII,PacI, AscI, XhoI and EcoNI.

C) Construction of the vector pRP T:

-   -   pRP O: a derivative of pRPA-RD-153 containing an HPPD expression        cassette, double histone promoter—TEV HPPD gene—Nos terminator.        To manufacture pRP O, pRPA-RD153 is digested with HindIII,        treated with Klenow and then redigested with NcoI in order to        remove the oxy gene and to replace it with the HPPD gene derived        from the plasmid pRP A by digesting with BstEII, treating with        Klenow and redigesting with NcoI.    -   pRP R: to obtain the plasmid, pRP O was digested with PvuII and        SacI, the chimeric gene was purified and then ligated into        pRPA-RD-185, itself digested with PvuII and SacI.    -   pRP T: it was obtained by ligating the chimeric gene derived        from pRP R after digesting with SacI and HindIII into the        plasmid pRPA-BL 150 alpha2 digested with the same enzymes        (European Application EP No. 0 508 909).

The chimeric gene of the vector pRP T therefore has the followingstructure:

Double histone TEV Coding region Nos terminator promoter of HPPD

D) Construction of the vector pRP V

-   -   pRP P: it is a derivative of pRPA-RD-7 (European Application EP        No. 0 652 286) containing the optimized transit peptide followed        by the HPPD gene. It was obtained by ligating the coding portion        of HPPD derived from pRP A by BstEII and NcoI digestion,        treatment with Klenow and of the plasmid pRPA-RD-7 itself        digested with SphI and AccI and treated with T4 DNAse        polymerase.    -   pRP Q: a derivative of pRPA-RD-153 containing an HPPD expression        cassette, double histone promoter−TEV−OTP HPPD gene−Nos        terminator. To construct it, the plasmid pRPA-RD-153 is digested        with SalI, treated with Klenow and then redigested with NcoI in        order to remove the oxy gene and replace it with the HPPD gene        derived from the plasmid pRP P by BstEII digestion, treatment        with Klenow and redigestion with NcoI.    -   pRP S: to obtain it, the plasmid pRP Q was digested with PvuII        and SacI in order to remove the chimeric gene which was ligated        into pRPA-RD-185 itself digested with PvuII and SacI.    -   pRP V: it was obtained by ligation of the chimeric gene derived        from pRP S after digestion with SacI and HindIII into the        plasmid pRPA-BL 150 alpha2 (European Application EP No. 0 508        909).

The chimeric gene of the vector pRP Q therefore has the followingstructure:

Double histone TEV OTP Coding region Nos terminator promoter of HPPD

EXAMPLE 3 Transformation of the Industrial Tobacco PBD6

To determine the efficiency of these two chimeric genes, they weretransferred into the industrial tobacco PBD6 according to thetransformation and regeneration techniques already described in EuropeanApplication EP No. 0 508 909.

1) Transformation:

The vector is introduced into the non oncogenic Agrobacterium EHA 101strain (Hood et al., 1987) carrying the cosmid pTVK 291 (Komori et al.,1986). The transformation technique is based on the procedure by HorshR. et al., (1985) Science, 227, 1229-1231.

2) Regeneration:

The regeneration of the PBD6 tobacco (source SEITA France) from foliarexplants is carried out on a Murashige and Skoog (MS) basal mediumcomprising 30 g/l of sucrose and 100 μg/ml of kanamycin. The foliarexplants are removed from greenhouse plants or in vitro and transformedaccording to the foliar disc technique (Science 1985, Vol. 227, p.1229-1231) in three successive stages: the first comprises the inductionof shoots on an MS medium supplemented with 30 g/l of sucrose containing0.05 mg/l of naphthylacetic acid (ANA) and 2 mg/l of benzylaminopurine(BAP) for 15 days. The shoots formed during this stage are thendeveloped by culturing on an MS medium supplemented with 30 g/l ofsucrose but containing no hormone, for 10 days. Some of the shoots thathave developed are then removed and they are cultured on MS rootingmedium with half the content of salts, vitamins and sugars andcontaining no hormone. After about 15 days, the rooted shoots areplanted in the soil. The plants obtained are called Co 17.

Upon leaving in vitro, the transformed tobacco plantlets wereacclimatized in a greenhouse (60% relative humidity, temperature: 20° C.at night and 23° C. during the day) for five weeks and then treated with4-[4-CF₃-2-(methylsulphonyl)benzoyl]-5-cyclopropylisoxazole.

The control tobacco, not transformed and treated with4-[4-CF₃-2-(methylsulphonyl)benzoyl]-5-cyclopropylisooxazole at dosesranging from 50 to 400 g/ha, develop chlorosis in about 72 hours, whichintensifies and develops into very pronounced necrosis within one week(covering about 80% of the terminal leaves).

After transformation, this same tobacco, which overexpresses the P.fluorescens HPPD, is very well protected against treatment with4-[4-CF₃-2-(methylsulphonyl)benzoyl]-5-cyclopropylisooxazole at a doseof 400 g/ha.

If the enzyme overexpressed is in the chloroplast, that is to say if thetransformation was made with the gene carried by the vector pRP V, thenthe plant is perfectly protected and shows no symptom.

EXAMPLE 4 Transformation of the Industrial Tobacco PBD6 with EPSPS GeneforConstruct 173

Isolation of a cDNA encoding a maize EPSPS:

The various stages which led to the production of maize EPSPS cDNA,which served as substrate for the introduction of the two mutations, aredescribed below. All the operations described below are given by way ofexamples and correspond to a choice made among the various methodsavailable to arrive at the same result. This choice has no effect on thequality of the result and, consequently, any suitable method may be usedby persons skilled in the art to arrive at the same result. Most of themethods for engineering DNA fragments are described in “CurrentProtocols in Molecular Biology” Volumes 1 and 2, Ausubel F. M. et al.,published by Green Publishing Associates and Wiley-Interscience (1989)(in the text that follows, the references to the protocols described inthis manual will be noted “ref. CPMB”). The operations regarding theDNA, which were carried out according to the protocols described in thismanual are, in particular, the following: ligation of the DNA fragments,treatments with Klenow DNA polymerase and T4 DNA polymerase, preparationof DNA from plasmids and λ bacteriophages, either as a minipreparationor as a maxipreparation, analyses of DNA and RNA according to theSouthern and Northern techniques respectively. Other methods describedin this manual were followed and only significant modifications oradditions to these protocols have been described below:

A1. Production of an EPSPS Fragment from Arabidopsis thaliana

a) Two 20-mer oligonucleotides of respective sequences:

5′-GCTCTGCTCATGTCTGCTCC-3′ 5′-GCCCGCCCTTGACAAAGAAA-3′

were synthesized from the sequence of an Arabidopsis thaliana EPSPS gene(Klee H. J. et al. (1987) Mol. Gen. Genet., 210, 437-442). These twooligonucleotides are respectively at position 1523 to 1543 and 1737 to1717 of the published sequence and in convergent orientation.

b) The total DNA from Arabidopsis thaliana (var. columbia) was obtainedfrom Clontech (catalogue reference: 6970-1)

c) 50 nanograms (ng) of DNA are mixed with 300 ng of each of theoligonucleotides and subjected to 35 amplification cycles with aPerkin-Elmer 9600 apparatus, under standard medium conditions foramplification which are recommended by the supplier. The resulting 204bp fragment constitutes the Arabidopsis thaliana EPSPS fragment.

2. Construction of a cDNA Library from a BMS Maize Cell Line.

a) 5 g of filtered cells are ground in liquid nitrogen and the totalnucleic acids extracted according to the method described by Shure etal., with the following modifications:

-   -   the pH of the lysis buffer is adjusted to pH=9.0;    -   after precipitation with isopropanol, the pellet is taken up in        water and after dissolution, adjusted to 2.5 M LiCl. After        incubation for 12 h at [lacuna] ° C., the 15-min centrifugation        pellet at 30,000 g and 4° C. is resolubilized. The precipitation        stage with LiCl is then repeated. The resolubilized pellet        constitutes the RNA fraction of the total nucleic acids.

b) The RNA-polyA+ fraction of the RNA fraction is obtained bychromatography on an oligo-dT cellulose column as described in “CurrentProtocols in Molecular Biology”.

c) Synthesis of double-stranded cDNA with synthetic EcoRI end: it isperformed according to the protocol of the supplier of the variousreagents necessary for this synthethis in the form of a kit: the “copykit” from the company In Vitrogen.

Two single-stranded and partially complementary oligonucleotides ofrespective sequences:

5′-AATTCCCGGG-3′

5′-CCCGGG-3′ (the latter being phosphorylated)

are ligated with the blunt ended double-stranded cDNA.

This ligation of the adaptors results in the creation of SmaI sitesattached to the double-stranded cDNA and of EcoRI sites in cohesive format each end of the double-stranded cDNA.

d) Creation of the library:

The cDNAs having the cohesive artifical EcoRI sites at their ends areligated with the cDNA from the bacteriophage λgt10 cut with EcoRI anddephosphorylated according to the protocol from the supplier New EnglandBiolabs.

One aliquot of the ligation reaction was encapsidated in vitro withencapsidation extracts: Gigapack Gold according to the instructions ofthe supplier, this library was titrated using the bacterium E. coliC600hfl. The library thus obtained is amplified and stored according tothe instructions of the same supplier and constitutes the EMS maize cellsuspension cDNA library.

3. Screening of the BMS Maize Cell Suspension cDNA Library with theArabidopsis thaliana EPSPS Probe:

The protocol followed is that of “Current Protocols in MolecularBiology” Volumes 1 and 2, Ausubel F. M. et al., published by GreenePublishing Associates and S (1989) (CPMB). Briefly, about 10⁶recombinant phages are plated on an LB dish at an average density of 100phages/cm². The lysis plagues are subcultured in duplicate on anAmersham Hybond N membrane.

h) The DNA was fixed on the filters by a 1600 kJ UV treatment(Stratalinker from Stratagene). The filters were prehybridized in:6×SSC/0.1% SDS/0.25 skimmed milk for 2 h at 65° C. The Arabidopsisthaliana EPSPS probe was labelled with ³²P-dCTP by “random priming”according to the instructions of the supplier (Kit Ready to Go fromPharmacia). The specific activity obtained is of the order of 10⁸ cpmper μg of fragment. After denaturation for 5 min at 100° C., the probeis added to the prehybridization medium and the hybridization iscontinued for 14 hours at 55° C. The filters are fluorographed for 48 hat −80° C. and with a Kodak XAR5 film and Amersham Hyperscreen RPNintensifying screens. The alignment of the positive spots on the filterwith the dishes from which they are derived makes it possible to remove,from the dish, zones corresponding to the phages exhibiting a positivehybridization response with the Arabidopsis thaliana EPSPS probe. Thisplating, transfer, hybridization and recovery stage is repeated untilall the spots on the dish of phages successively purified prove 100%positive in hybridization. One lysis plaque per independent phage isthen removed from the diluent λ medium (Tris-Cl pH=7.5; 10 mM MgSO₄; 0.1M NaCl, 0.1% gelatin), these phages constituting in solution thepositive BMS maize cell suspension EPSP clones.

4. Preparation and Analysis of the DNA from the BMS Maize CellSuspension EPSPS Clones.

About 5×10⁸ phages are added to 20 ml of C600 hfl bacteria at 2 OD 600nm/ml and incubated for 15 minutes at 37° C. This suspension is thendiluted in 200 ml of bacterial growth medium in a 1 l Erlenmeyer flaskand stirred in a rotary shaker at 250 rpm. The lysis is assessed byclarification of the medium, corresponding to a lysis of the turbidbacteria and occurs after shaking for about 4 h. This supernatant isthen treated as described in “Current Protocols in Molecular Biology”.The DNA obtained corresponds to the BMS maize cell suspension EPSPclones.

One to two μg of this DNA are cut with EcoRI and separated on a 0.8%LGTA/TBE agarose gel (ref. CPMB). A final verification consists inensuring that the purified DNA indeed exhibits a hybridization signalwith the Arabidopsis thaliana EPSPS probe. After electrophoresis, theDNA fragments are transferred onto an Amersham Hybond N membraneaccording to the Southern protocol described in “Current Protocols inMolecular Biology”. The filter is hybridized with the Arabidopsisthaliana EPSPS probe according to the conditions described in paragraph3 above. The clone exhibiting a hybridization signal with theArabidopsis thaliana EPSPS probe and containing the longest EcoRIfragment has a gel-estimated size of about 1.7 kbp.

5. Production of the pRPA-ML-711 Clone:

Ten μg of DNA from the phage clone containing the 1.7 kbp insert aredigested with EcoRI and separated on a 0.8% LGTA/TBE agarose gel (ref.CPMB). The gel fragment containing the 1.7 kbp insert is excised fromthe gel by BET staining and the fragment is treated with β-agaraseaccording to the protocol of the supplier New a Biolabs. The DNApurified from the 1.7 kbp fragment is ligated at 12° C. for 14 h withthe DNA from the plasmid pUC 19 (New England Biolabs) cut with EcoRIaccording to the ligation protocol described in “Current Protocols inMolecular Biology”. Two μl of the above ligation mixture are used forthe transformation of an aliquot of electrocompetent E. coli DH10B; thetransformation is performed by electroporation using the followingconditions: the mixture of competent bacteria and of ligation medium isintroduced into an electroporation cuvette 0.2 cm thick (Biorad)previously cooled to 0° C. The physical conditions for theelectroporation using an electroporator of Biorad brand are 2,500 volts,25 μFarad and 200Ω. Under these conditions, the mean condenser dischargetime is of the order of 4.2 milliseconds. The bacteria are then taken upin 1 ml of SOC medium (ref. CPMB) and stirred for 1 hour at 200 rpm on arotary shaker in 15 ml Corning tubes. After plating on LB/agar mediumsupplemented with 100 μg/ml of carbenicillin, the minipreparations ofthe bacterial clones which have grown overnight at 37° C. are preparedaccording to the protocol described in “Current Protocols in MolecularBiology”. After digesting the DNA with EcoRI and separating byelectrophoresis on a 0.8% LGTA/TBE agarose gel (ref. CPMB), the cloneshaving a 1.7 kbp insert are preserved. A final verification consists inensuring that the purified DNA indeed exhibits a hybridization signalwith the Arabidopsis thaliana EPSPS probe. After electrophoresis, theDNA fragments are transferred onto an Amersham Hybond N membraneaccording to the Southern protocol described in “Current Protocols inMolecular Biology”. The filter is hybridized with the Arabidopsisthaliana EPSPS probe according to the conditions described in paragraph3 above. The plasmid clone having a 1.7 kbp insert and hybridizing withthe Arabidopsis thaliana EPSPS probe was prepared on a larger scale andthe DNA resulting from lysing the bacteria purified on a CsCl gradientas described in “Current Protocols in Molecular Biology”. The purifiedDNA was partially sequenced with a Pharmacia kit according to theinstructions of the supplier and using, as primers, the reverse anddirect M13 universal primers ordered from the same supplier. The partialsequence determined covers about 0.5 kbp. The derived amino acidsequence in the region of the mature protein (about 50 amino acidresidues) exhibits 100% identity with the corresponding Amino sequenceof the mature maize EPSPS described in American Patent U.S. Pat. No.4,971,908). This clone corresponding to a 1.7 kbp EcoRI fragment of theBMS maize cell suspension EPSP DNA was called pRPA-ML-711. The completesequence of this clone was determined on both strands using thePharmacia kit protocol and by synthesizing oligonucleotides which arecomplementary and of opposite direction every 250 bp approximately. Thecomplete sequence of this 1713 bp clone obtained is presented in SEQ IDNo. 2.

6. Production of the pRPA-ML-715 Clone:

The analysis of the sequence of the pRPA-ML-711 clone and in particularcomparison of the derived amino acid sequence with that from maize showsa 92 bp sequence extension upstream of the GCG codon encoding theNH₂-terminal alanine of the mature part of maize EPSPS (American PatentU.S. Pat. No. 4,971,908). Likewise, a 288 bp extension downstream of theAAT codon encoding the COOH-terminal asparagine of the mature part ofmaize EPSPS (American Patent U.S. Pat. No. 4,971,908) is observed. Thesetwo parts may correspond, for the NH₂-terminal extension, to a portionof the sequence of a transit peptide for plastid localization and, forthe COOH-terminal extension, to the 3′ untranslated region of the cDNA.

To obtain a cDNA encoding the mature part of the maize EPSPS cDNA, asdescribed in U.S. Pat. No. 4,971,908, the following operations werecarried out:

a) Elimination of the untranslated 3′ region: construction ofpRPA-ML-712:

The pRPA-ML-711 clone was cut with the restriction enzyme AseI and theends resulting from this cut made blunt by treating with the Klenowfragment of DNA polymerase I according to the protocol described inCPMB. A cut with the restriction enzyme SacII was then made. The DNAresulting from these operations was separated by electrophoresis on a 1%LGTA/TBE agarose gel (ref. CPMB).

The gel fragment containing the 0.4 kbp “AseI-blunt ends/SacII” insertwas excised from the gel and purified according to the protocoldescribed in paragraph 5 above. The DNA of the clone pRPA-ML-711 was cutwith the restriction enzyme HindIII situated in the polylinker of thecloning vector pUC19 and the ends resulting from this cut were madeblunt by treating with the Klenow fragment of DNA polymerase I. A cutwith the restriction enzyme SacII was then made. The DNA resulting fromthese manipulations was separated by electrophoresis on a 0.7% LGTA/TBEagarose gel (ref. CPMB).

The gel fragment containing the HindIII-blunt ends/SacII insert of about3.7 kbp was excised from the gel and purified according to the protocoldescribed in paragraph 5 above.

The two inserts were ligated, and 2 μl of the ligation mixture were usedto transform E. coli DH1OB as described above in paragraph 5.

The plasmid DNA content of the various clones is analysed according tothe procedure described for pRPA-ML-711. One of the plasmid clonesretained contains an EcoRI-HindIII insert of about 1.45 kbp. Thesequence of the terminal ends of this clone shows that the 5′ end of theinsert corresponds exactly to the corresponding end of pRPA-ML-711 andthat the 3′ terminal end has the following sequence:

“5′-AATTAAGCTCTAGAGTCGACCTGCAGGCATGCAAGCTT-3′”.

The sequence underlined corresponds to the codon for the COOH-terminalamino acid asparagine, the next codon corresponding to the translationalstop codon. The downstream nucleotides correspond to sequence elementsof the pUC19 polylinker. This clone comprising the pRPAML-711 sequenceup to the site for termination of translation of mature maize EPSPS andfollowed by pUC 19 polylinker sequences up to the HindIII site wascalled pRPA-ML-712.

b) Modification of the 5′ end of pRPA-ML-712: construction ofpRPA-ML-715

The pRPA-ML-712 clone was cut with the restriction enzymes PstI andHindIII. The DNA resulting from these manipulations was separated byelectrophoresis on a 0.8% LGTA/TBE agarose gel (ref. CPMB). The gelfragment containing the 1.3 kbp PstI/EcoRI insert was excised from thegel and purified according to the protocol described in paragraph 5above. This insert was ligated in the presence of an equimolar quantityof each of the two partially complementary oligonucleotides of sequence:

Oligo 1: 5′-GAGCCGAGCTCCATGGCCGGCGCCGAGGAGATCGTGCTGCA-3′ Oligo 2:5′-GCACGATCTCCTCGGCGCCGGCCATGGAGCTCGGCTC-3′

and in the presence of DNA from the plasmid pUC19 digested with therestriction enzymes BamHI and HindIII.

Two μl of the ligation mixture served to transform E. coli DH1OB asdescribed above in paragraph 5. After analysis of the plasmid DNAcontent of various clones according to the procedure described above inparagraph 5, one of the clones having an insert of about 1.3 kbp waspreserved for subsequent analyses. The sequence of the terminal 5′ endof the clone retained shows that the DNA sequence in this region is thefollowing: pUC19 polylinker sequence of the EcoRI to BamHI sites,followed by the sequence of the oligonucleotides used during thecloning, followed by the remainder of the sequence present inpRPAML-712. This clone was called pRPA-ML-713. This clone has amethionine codon ATG included in an NcoI site upstream of the N-terminalalanine codon of the mature EPSP synthase. Furthermore, the alanine andglycine codons of the N-terminal end were conserved, but modified on thethird variable base: initial GCGGGT gives modified GCCGGC.

The clone pRPA-ML-713 was cut with the restriction enzyme HindIII andthe ends of this cut made blunt by treating with the Klenow fragment ofDNA polymerase I. A cut with the restriction enzyme SacI was then made.The DNA resulting from these manipulations was separated byelectrophoresis on a 0.8% LGTA/TBE agarose gel (ref. CPMB). The gelfragment containing the 1.3 kbp “HindIII-blunt ends/SacI” insert wasexcised from the gel and purified according to the protocol described inparagraph 5 above. This insert was ligated in the presence of DNA fromthe plasmid pUC19 digested with the restriction enzyme XbaI and the endsof this cut made blunt by treating with the Klenow fragment of DNApolymerase I. A cut with the restriction enzyme SacI was then made. Twoμl of the ligation mixture were used to transform E. coli DH1OB asdescribed above in paragraph 5. After analysis of the plasmid DNAcontent of various clones according to the procedure described above inparagraph 5, one of the clones having an insert of about 1.3 kbp waspreserved for subsequent analyses. The sequence of the terminal ends ofthe clone retained shows that the DNA sequence is the following: pUC19polylinker sequence of the EcoRI to SacI sites, followed by the sequenceof the oligonucleotides used during the cloning, deleted of the 4 bpGATCC of oligonucleotide 1 described above, followed by the remainder ofthe sequence present in pRPA-ML-712 up to the HindIII site and sequenceof the pUC19 polylinker from XbaI to HindIII. This clone was calledpRPA-ML-715.

7) Production of a cDNA Encoding a Mutated Maize EPSPS

All the mutagenesis stages were performed with the U.S.E. mutagenesiskit from Pharmacia, following the instructions of the supplier. Theprinciple of this mutagenesis system is the following: the plasmid DNAis heat-denatured and annealed in the presence of a molar excess, on theone hand, of the mutagenesis oligonucleotide and, on the other hand, ofan oligonucleotide which makes it possible to eliminate a uniquerestriction enzyme site present in the polylinker. After the annealingstage, the synthesis of the complementary strand is carried out by theaction of T4 DNA polymerase in the presence of T4 DNA ligase and proteinfrom gene 32 in an appropriate buffer provided. The synthetic product isincubated in the presence of the restriction enzyme, whose site issupposed to have disappeared by mutagenesis. The E. coli strain having,in particular, the mutS mutation is used as host for the transformationof this DNA. After growth in liquid medium, the total plasmid DNA isprepared, incubated in the presence of the restriction enzyme previouslyused. After these treatments, the E. coli DH1OB strain is used as hostfor the transformation. The plasmid DNA of the clones isolated isprepared and the presence of the mutation introduced is verified bysequencing.

A) Sequence or site modifications without any effect a priori on theresistance character of maize EPSPS to products which are competitiveinhibitors of the activity of EPSP synthase: elimination of an internalNcoI site from pRPA-ML-715.

The sequence of pRPA-ML-715 is numbered arbitrarily by placing the firstbase of the N-terminal alanine codon GCC in position 1. This sequencehas an NcoI site at position 1217. The site modification oligonucleotidehas the sequence:

5′-CCACAGGATGGCGATGGCCTTCTCC-3′.

After sequencing according to the references given above, the sequenceread after mutagenesis corresponds to that of the oligonucleotide used.The NcoI site was indeed eliminated and the translation into amino acidsin this region conserves the initial sequence present in pRPA-ML-715.

This clone was called pRPA-ML-716.

The 1340 bp sequence of this clone is presented SEQ ID No. 3 and SEQ IDNo. 4.

B) Sequence modifications allowing an increase in the resistancecharacter of maize EPSPS to products which are competitive inhibitors ofEPSP synthase activity.

The following oligonucleotides were used:

a) Thr 102 → Ile mutation. 5′-GAATGCTGGAATCGCAATGCGGCCATTGACAGC-3′b) Pro 106 → Ser mutation. 5′-GAATGCTGGAACTGCAATGCGGTCCTTGACAGC-3′c) Gly 101 → Ala and Thr 102 → Ile mutations.5′-CTTGGGGAATGCTGCCATCGCAATGCGGCCATTG-3′ d) Thr 102 → Ile and Pro 106 →Ser mutations. 5′-GGGGAATGCTGGAATCGCAATGCGGTCCTTGACAGC-3′

After sequencing, the sequence read after mutagenesis on the threemutated fragments is identical to the parental DNA sequence pRPA-ML-716with the exception of the mutagenized region which corresponds to thatof the mutagenesis oligonucleotides used. These clones were called:pRPA-ML-717 for the Thr 102→Ile mutation, pRPA-ML-718 for the Pro106→Ser mutation, pRPA-ML-719 for the Gly 101→Ala and Thr 102→Ilemutations and pRPA-ML-720 for the Thr 102→Ile and Pro 106→Ser mutations.

The 1340 bp sequence of pRPA-ML-720 is presented SEQ ID No. 5 and SEQ IDNo. 6.

The 1395 by NcoI-HindIII insert forms the basis of all the constructsused for the transformation of the plants for the introduction of theresistance to herbicides which are competitive inhibitors of EPSPS andin particular the resistance to glyphosate. This insert will be calledin the remainder of the descriptions “the double maize EPSPS mutant”.

B Glyphosate Tolerance of the Various Mutants in vitro.

2.a: Extraction of EPSP Synthase.

The various EPSP synthase genes are introduced in the form of anNcoI-HindIII cassette into the plasmid vector pTrc99a (Pharmacia, ref:27-5007-01) cut with NcoI and HindIII. The recombinant E. coli DH1OBoverexpressing the various EPSP synthases are sonicated in 40 ml ofbuffer per 10 g of culotted cells and washed with this same buffer (200mM Tris-HCl pH 7.8, 50 mM mercaptoethanol, 5 mM EDTA and 1 mM PMSF), towhich 1 g of polyvinylpyrrolidone is added. The suspension is stirredfor 15 minutes at 4° C. and then centrifuged for 20 minutes at 27,000 gand at 4° C.

The supernatant is supplemented with ammonium sulphate so as to bringthe solution to 40% saturation with ammonium sulphate. The mixture iscentrifuged for 20 minutes at 27,000 g and at 4° C. The new supernatantis supplemented with ammonium sulphate so as to bring the solution to70% saturation with ammonium sulphate. The mixture is centrifuged for 30minutes at 27,000 g and at 4° C. The EPSP synthase present in thisprotein pellet is taken up in 1 ml of buffer (20 mM Tris-HCl pH 7.8 and50 mM mercaptoethanol). This solution is dialysed overnight against twolitres of this same buffer at 4° C.

2.b: Enzymatic Activity.

The activity of each enzyme as well as its resistance to glyphosate ismeasured in vitro over 10 minutes at 37° C. in the following reactionmixture: 100 mM maleic acid pH 5.6, 1 mM phosphoenol pyruvate, 3 mMshikimate-3-phosphate (prepared according to Knowles P. F. and SprinsonD. B., 1970, Methods in Enzymol., 17A, 351-352 from Aerobacter aerogenesstrain ATCC 25597) and 10 mM potassium fluoride. The enzymatic extractis added at the last moment after the addition of glyphosate whose finalconcentration varies from 0 to 20 mM.

The activity is measured by assaying the phosphate liberated accordingto the technique of Tausky H. A. and Shorr E., 1953, J. Biol. Chem.,202, 675-685.

Under these conditions, the wild-type (WT) enzyme is 85% inhibitedstarting from the concentration of 0.12 mM glyphosate. At thisconcentration, the mutant enzyme known as Ser106 is only 50% inhibitedand the other three mutants Ile 102, Ile 102/Ser 106, Ala 101/Ile 102are not or not strongly inhibited.

The glyphosate concentration should be multiplied by ten, that is to say1.2 mM, in order to inhibit the mutant enzyme Ile 102 bp 50%, themutants Ile 102/Ser 106, Ala/Ile and Ala still not being inhibited.

It should be noted that the activity of the Ala/Ile and Ala mutants isnot inhibited up to concentrations of 10 mM glyphosate, and that that ofthe mutant Ile 102/Ser 106 is not reduced even when the glyphosateconcentration is multiplied by 2, that is to say 20 mM.

C Resistance of the Transformed Tobacco Plants.

0-1 Construction of the plasmids:

pRPA-RD-124: Addition of a “nos” polyadenylation signal to pRPA-ML-720,previously obtained, with creation of a cloning cassette containing themaize double mutant EPSPS gene (Thr 102→Ile and Pro 106→Ser).pRPA-ML-720 is digested with HindIII, treated with the Klenow fragmentof DNA polymerase from E. coli in order to produce a blunt end. A seconddigestion is carried out with NcoI and the EPSPS fragment is purified.The EPSPS gene is then ligated with purified pRPA-RD-12 (a cloningcassette containing the nopaline synthase polyadenylation signal) inorder to give pRPA-RD-124. In order to obtain the useful purified vectorpRPA-RD-12, it was necessary that the latter be previously digested withSall, treated with Klenow DNA polymerase and then digested a second timewith NcoI.

pRPA-RD-125: Addition of an optimized transit peptide (OTP) topRPA-RD-124 with creation of a cloning cassette containing the targetedEPSPS gene on the plasmids. pRPA-RD-7 (European Patent Appliction EP 652286) is digested with SphI, treated with T4 DNA polymerase, and thendigested with SpeI and the OTP fragment is purified. This OTP fragmentis cloned into pRPA-RD-124 which was previously digested with NcoI,treated with Klenow DNA polymerase in order to remove the 3′ protrudingpart, and then digested with SpeI. This clone was then sequenced inorder to ensure correct translational fusion between OTP and the EPSPSgene. pRPA-RD-125 is thus obtained.

pRPA-RD-159: Addition of the Arabidopsis H4A748 double histone promoter(Patent Application EP 507 698) to pRPA-RD-125 with creation of acassette for expression in plants for the expression of the gene“OTP-double mutant EPSPS gene” in dicotyledonous tissues. pRPA-RD-132 (acassette containing the H4A748 double promoter (Patent Application EP507 698)) is digested with NcoI and SacI. The purified fragment of thepromoter is then cloned into what was digested with EcoI and SacI.

pRPA-RD-173: Addition of the gene “promoter of the H4A748-OTP-doublemutant EPSPS gene” of pRPA-RD-159 into the plasmid pRPA-BL-150A(European Patent Application 508 909) with creation of an Agrobacteriumtumefaciens transformation vector. pRPA-RD-159 is digested with NotI andtreated with the Klenow polymerase. This fragment is then cloned intopRPA-BL-150A with SmaI.

1-1-Transformation.

The vector pRPA-RD-173 is introduced into the Agrobacterium tumefaciensEHA101 strain (Hood et al., 1987) carrying the cosmid pTVK291 (Komari etal., 1986). The transformation technique is based on the procedudre ofHorsh et al. (1985).

1-2-Regeneration.

The regeneration of the PBD6 tobacco (source SEITA France) from foliarexplants is carried out on a Murashige and Skoog (MS) basal mediumcomprising 30 g/l of sucrose and 200 μg/ml of kanamycin. The foliarexplants are removed from greenhouse plants or in vitro and transformedaccording to the foliar disc technique (Science, 1985, Vol. 227, p.1229-1231) in three successive stages: the first comprises the inductionof shoots on an MS medium supplemented with 30 g/l of sucrose containing0.05 mg/l of naphthylacetic acid (ANA) and 2 mg/l of benzylaminopurine(BAP) for 15 days. The shoots formed during this stage are thendeveloped by culturing on an MS medium supplemented with 30 g/l ofsucrose but containing no hormone, for 10 days. The shoots that havedeveloped are then removed and they are cultured on MS rooting mediumwith half the content of salts, vitamins and sugar and containing nohormone. After about 15 days, the rooted shoots are planted in the soil.

1-3-Resistance to Glyphosate.

Twenty transformed plants were regenerated and placed in a greenhousefor the construct pRPA-RD-173. These plants were treated in a greenhouseat the 5-leaf stage with an aqueous suspension of RoundUp correspondingto 0.8 kg of glyphosate active substance per hectare.

The results correspond to the observation of phytotoxicity indices noted3 weeks after the treatment. Under these conditions, it is observed thatthe plants transformed with the construct pRPA-RD-173 exhibit a verygood tolerance whereas the nontransformed control plants are completelydestroyed.

These results show clearly the improvement made by the use of a chimericgene according to the invention for the same gene encoding glyphosatetolerance.

EXAMPLE 5 Transformation of the Industrial Tobacco PBD6, with theNitrilase Gene (for→construct 238)

This tobacco is obtained according to the teaching of EuropeanApplication No. 0 337 899 page 6 line 50 and subsequent pages from theconstruct 238, which is that described under the name pRPA-BL 238.

EXAMPLE 6 Crossing by Pollination

The lines Co 17, 173 and 238 are crossed respectively by pollination ina greenhouse:

-   Co 17 with 238 in order to obtain PBD6 tobacco plants to be tested    for the double tolerance to isoxaflutole and to bromoxynil (“plants    HPPD+OXY”) and-   Co 17 with 173 in order to obtain PBD6 tobacco plants to be tested    for double tolerance to isoxaflutole and glyphosate (“plants    HPPD+EPSPS”).

The three lines are homozygous with respect to the relevant gene:consequently, the progeny is hemizygous for each of the two genesintroduced by crossing.

The crossed plants are obtained after six weeks.

EXAMPLE 7 Measurement of the Tolerance of Tobacco in PostemergenceTreatment with Isoxaflutole and Postemergence Treatment with Bromoxynilor Glyphosate

In this trial, each test is performed on a sample of 10 plants, 10plants being kept untreated.

All the treatments are performed by spraying at the rate of 500 l ofspraying mixture per hectare.

For the postemergence treatment, sowing is performed and then the plantsare transplanted in 9 cm×9 cm pots.

The postemergence treatments are carried out at a well developed stage(3-4 leaves). Batches of plants, respectively wild-type and geneticallytransformed, obtained above are divided into several parts, with:

-   a) an untreated batch,-   b) other batches which are treated respectively with one herbicide    alone,    -   isoxaflutole in postemergence, at two doses (200 and 400 g/ha        respectively),    -   bromoxynil in postemergence at two doses (400 and 800 g/ha        respectively),    -   glyphosate in postemergence at two doses (800 and 1200 g/ha        respectively),-   c) other batches which are treated respectively with two herbicides,    in postemergence, in a freshly prepared mixture:    -   isoxaflutole and bromoxynil at two doses (200/400 and 400/800        g/ha respectively)    -   isoxaflutole and glyphosate at two doses (200/800 and 400/1200        g/ha respectively).

The treatments are carried out with the following formulations: 75%isoxaflutole, bromoxynil (commercial product PARDNER) in octanoate form,as an emulsifiable concentrate at 225 g/l and glyphosate (Roundup).

Under these conditions, the following phytotoxicities are observed 17days after the treatment, expressed as percentage destruction indicatedin the following table, as well as the number of plants per batch andthe doses of herbicide(s) expressed in gram of active substance perhectare:

Postemergence Treatment with Isoxaflutole and Postemergence Treatmentwith Bromoxynil or Glyphosate

Plants with tolerance gene Herbicide HPPD + HPPD + WITHOUT = in g/l *OXY * EPSPS * wild-type Controls 10 10 10 isoxaflutole 200 20 4% 20 2%10 75% alone 400 20 5% 20 3% 85% bromoxynil 400 10 3% 10 0% alone 800 100% 10 0% glyphosate 800 20 0% 10 100% alone 1200 20 0% 10 100%isoxaflutole 200 20 20% 10 100% +bromoxynil 400 isoxaflutole 400 20 30%10 100% +bromoxynil 800 isoxaflutole 200 40 5% 10 100% +glyphosate 800isoxaflutole 400 40 10% 10 100% +glyphosate 1200 * number of plants

EXAMPLE 8

With the aim of studying whether the Pseudomonas fluorescens HPPD genecan be used as marker gene during the “transformation-regeneration”cycle of a plant species, the tobacco was transformed with the chimericgene composed of the HPPD gene and the EPSPS gene doubly mutated forresistance to glyphosate and transformed plants resistant to bothisoxaflutole and glyphosate were obtained after selection onisoxaflutole.

Materials and Methods and Results

The chimeric gene pRP 2012 described below is transferred into the PBD6industrial tobacco according to the transformation and regenerationprocedures already described in European Application EP No. 0 508 909.

The chimeric gene of the vector pRP 2012 has the following structureA-B, in which:

A is:

Double histone TEV OTP Coding region Nos terminator promoter of HPPD

and B is:

Double histone TEV OTP Coding region Nos terminator promoter of EPSPS

such as that used in the vector pRPA-RD-173.

The chimeric gene pRP 2012 is introduced into the tobacco.

1) Transformation:

The vector is introduced into the non-oncogenic Agrobacterium EHA 101strain (Hood et al., 1987) carrying the cosmid pTVK 291 (Komari et al.,1986). The transformation technique is based on the procedure by Horshet al., (1985).

2) Regeneration:

The regeneration of the PBD6 tobacco (source SEITA France) from foliarexplants is carried out on a Murashige and Skoog (MS) basal mediumcomprising 30 g/l of sucrose and 350 mg/l of cefotaxime and 1 mg/l ofisoxaflutole. The foliar explants are removed from greenhouse plants orin vitro and transformed according to the foliar disc technique (Science1985, Vol. 227, p. 1229-1231) in three successive stages: the firstcomprises the induction of shoots on an MS medium supplemented with 30g/l of sucrose containing 0.05 mg/l of naphthylacetic acid (ANA) and 2mg/l of benzylaminopurine (BAP) for 15 days and 1 mg/l of isoxaflutole.The green shoots formed during this stage are then developed byculturing on an MS medium supplemented with 30 g/l of sucrose and 1 mg/lof isoxaflutole but containing no hormone, for 10 days. The shoots thathave developed are then removed and they are cultured on MS rootingmedium with half the content of salts, vitamins and sugars and 1 mg/l ofisoxaflutole and containing no hormone. After about 15 days, the rootedshoots are planted in the soil.

All the plants obtained according to this protocol are analysed by PCRwith primers specific for P. fluorescens HPPD. This PCR analysis made itpossible to confirm that all the plants thus obtained have indeedintegrated the HPPD gene and that they are tolerant to both isoxaflutoleand glyphosate, under the conditions described in Example 7.

In conclusion, this trial confirms that the HPPD gene may be used asmarker gene and that, combined with this gene, isoxaflutole may be agood selection agent.

EXAMPLE 9 Plant with an HPPD Gene and a Bar Gene Resistant to bothIsoxaflutole and Phosphinothricin

1. Construction of a Chimeric Gene with an HPPD Sequence:The plasmid pRPA-RD-1004 represented in FIG. 4 is obtained by insertingthe chimeric gene for resistance to the isoxazoles into the 2686 bpplasmid pUC19, marketed by New England Biolabs (Yannish-Perron, C.Viera, J. and Massing, J. (1985) Gene 33, 103-119) and containing theresistance to ampicillin.

The various elements of the chimeric gene are, in the direction oftranslation:

-   -   the 1020 bp maize H3C4 histone promoter described in the        application EP 0 507 698;    -   the intron of the maize alcohol dehydrogenase 1 gene described        by Sachs M. et al., Genetics 113: 449-467 (1986) and consisting        of 536 bp    -   the optimized transit peptide (OTP) described in Patent        Application EP 0 508 909; this OTP consists of the 171 bp of the        transit peptide of the small subunit of ribulose        1,5-bisphosphate carboxylase/oxygenase from Helianthus annuus        (Waksman G. et al., 1987, Nucleics acids Res. 15: 7181) followed        by the 66 bp of the mature part of the small subunit of ribulose        1,5-bisphosphate carboxylase/oxygenase from Zea mays (Lebrun at        al., 1987, Nucleics acids Res. 15: 4360), themselves followed by        the 150 bp of the transit peptide of the small subunit of        ribulose 1,5-bisphosphate carboxylase/oxygenase from Zea mays        (Lebrun at al., 1987, Nucleics acids Res. 15: 4360); the whole        is therefore 387 bp;    -   the coding region of the Pseudomonas fluorescens HPPD described        above;    -   the terminator of the nopaline synthase (nos) gene        (polyadenylation region of the nos gene isolated from pTi 37,        250 bp (Bevan M. et al., Nucleics Acids Res. 11: 369-385);

2. Construction of a Chimeric Gene for Tolerance to Phosphinothricin(Bar Gene):

Phosphinothricin acetyl transferase (PAT) encoded by the bar gene is anenzyme which inactivates a herbicide, phosphinothricin (PPT). PPTinhibits the synthesis of glutamine and causes rapid accumulation ofammonia in the cells, leading to their death (Tachibana et al., 1986).

The plasmid used to introduce the tolerance to phosphinothricin asselection agent is obtained by inserting the chimeric gene pDM 302 intothe 2462 bp vector pSP72, marketed by Promega Corp. (Genbank/DDBJdatabase accession number X65332) and containing the gene for resistanceto amplicillin.

The 4700 bp plasmid pDM 302 has been described by Cao, J., et al., PlantCell Report 11: 586-591 (1992).

The various elements of this plasmid are:

-   -   the promoter of the rice actin gene described by McElroy D. et        al., Plant Molecular Biology 15: 257-268 (1990) consisting of        840 bp;    -   the first exon of the rice actin gene consisting of 80 bp;    -   the first intron of the rice actin gene consisting of 450        bp;—the coding region of the bar gene of 600 bp excised from the        plasmid pIJ41404 described by White J. et al., Nuc. Acids res.        18: 1862 (1990);    -   the terminator of the nopaline synthase (nos) gene        (polyadenylation region of the nos gene isolated from pTi 37,        250 bp (Bevan M. et al., Nucleics Acids Res. 11: 369-385).

3. Transformation:

The bombardment technique is used to introduce the genetic construct.The plasmids are purified on a Qiagen column and coprecipitated onparticles of tungsten M10 according to the Klein process (Nature 327:70-73, 1987).

A mixture (?) of metallic particles and of the two plasmids describedabove is then bombarded on maize embryogenesis cells according to theprotocol by (???)

4. Regeneration and Use of the Bar Gene as Selection Agent:

The bombarded calli are selected on glufosinate until green sectorsappear. The positive calli (?) are then converted into somatic embryos(prior art conditions or reference?) and then placed under conditionspromoting germination (prior art conditions or reference?). The youngplants are transferred into a greenhouse for the production of seeds(prior art conditions or reference?).

The molecular analyses (prior art conditions or reference? PCR?) carriedout on these plants show that:

-   -   at least 4 calli selected on phosphinothricin generated plants        showing the presence of the HPPD gene by PCR;    -   at least 5 calli selected on phosphinothricin generated plants        showing the presence of the HPPD gene by Southern blotting;    -   at least 5 calli selected on phosphinothricin generated plants        showing the presence of the recombinant protein by western        blotting:    -   the HPPD chimeric gene and the heterologous protein are absent        from the nontransformed calli.

These results show the efficiency of the bar chimeric gene for theselection of the transformed calli containing another gene of agronomicinterest.

5. Analysis of the Progeny of the Transformed Plants

The transformed plants obtained above produced pollen, assumed in partto be transgenic, which fertilized ovules from a nontransgenic wild-typemaize. The seeds obtained are selected on sand after treating withisoxaflutole.

The selection protocol is the following: 800 ml of Fontainebleau sandare placed in a tub with sides 15×20 cm. These tubs are then sprayedwith water and kept hydrated by supplying a nutritive solutionconsisting of 5 ml of Quinoligo (Quinoline) per litre of water. Twentymaize seeds are placed on the tubs, which are then treated withisoxaflutole by spraying at the rate of 100 to 200 g of active substanceper hectare (300 or 600 μg of active substance per tub). The tubs arethen placed in culture in a greenhouse.

The results obtained are assembled in the following table:

Isoxa- Number of Number of Number of Number of flutole seeds germinateddead surviving Genotypes (g/ha) sown plants plants plants nontrans- 0 2020 0 20 genic 100 20 20 20 0 261 2B 100 10 10 5 5 459 200 10 9 4 5 2612D2 100 10 9 6 3 200 10 10 7 3 261 2A2 100 10 5 3 2 200 10 7 7 0

These results show the efficiency of the HPPD gene for the selection ofresistant maize plants. They also show that the overexpression ofPseudomonas HPPD in maize tissues confers the tolerance to isoxaflutoleon them.

The sequences illustrated are the following:

SEQ ID No. 1

Sequence of the HPPD Gene from Pseudomonas fluorescens A32.

SEQ ID No. 2

Sequence of the Arabidopsis thaliazxa EPSPS cDNA

SEQ ID No. 3 and 4

Sequences, respectively, of the gene and of the protein for the mutatedmaize EPSPS, 1340 bp portion of the clone pRPA-ML-716

SEQ ID No. 5 and SEQ ID No. 6

Sequences, respectively, of the gene and of the protein for the mutatedmaize EPSPS, 1340 bp portion of the clone pRPA-ML-720

The figures below are given as a guide to illustrate the invention.

FIG. 1 represents the protein sequence of the HPPD from Pseudomonas sp.strain P. J. 874 and the theoretical nucleotide sequence of thecorresponding coding part; the five oligonucleotides chosen to performthe amplification of a portion of this coding region are symbolized bythe five arrows.

FIG. 2 represents the map of the plasmid with the 7 kb genomic DNAfragment containing the HPPD gene from P. fluorescens A32.

FIG. 3 gives the comparison of the amino acid sequences of the HPPD fromP. fluorescens A32 and of the HPPD from Pseudomonas sp strain P. J. 874(only the amino acids diverging between the two sequences are indicated)as well as the consensus sequence.

1-21. (canceled)
 22. A process for producing plants with multipleherbicide tolerance by transgenesis of the plants, comprising insertinginto several cells respectively one of at least two basic genes, thebasic genes each containing regulatory elements necessary for itstranscription in plants and a coding sequence encoding an enzymeconferring on plants tolerance to a herbicide, wherein said at least twobasic genes comprise first and second basic genes, said first basic genecomprising a coding sequence encoding a mutated HPPD and said secondbasic gene comprising a second coding sequence encoding an enzymeconferring on plants tolerance to a herbicide; regenerating plants fromsaid cells; and crossing said plants in order to obtain plants withmultiple tolerance to field application rates of said herbicides.
 23. Aprocess for the herbicidal treatment of plants comprising applying atleast two herbicides at field application rates to a plant comprising atleast two basic genes comprising first and second basic genes, saidfirst basic gene comprising regulatory elements necessary for itstranscription in plants and a coding sequence encoding a mutated HPPD,and said second basic gene comprising regulatory elements necessary forits transcription in plants and a second coding sequence encoding anenzyme conferring on plants tolerance to a herbicide.
 24. The processaccording to claim 23, characterized in that three herbicides areapplied.
 25. The process according to claim 23, characterized in thatone of the herbicides is an HPPD inhibitor.
 26. The process according toclaim 23 characterized in that both herbicides are appliedsimultaneously.
 27. The process according to claim 26, characterized inthat both herbicides are applied in the form of a single compositionready to use.
 28. The process according to claim 26, characterized inthat both herbicides are applied in the form of a freshly preparedmixture.
 29. The process according to claim 23, characterized in thatboth herbicides are applied in succession.
 30. The process according toclaim 25, characterized in that the herbicide inhibiting HPPD isisoxaflutole.
 31. The process according to claim 25, characterized inthat the herbicide inhibiting HPPD is sulcotrione.
 32. The processaccording to claim 23, characterized in that the herbicide belongs tothe dihydroohydroxybenzonitrile family.
 33. The process according toclaim 32, characterized in that the herbicide is bromoxynil.
 34. Theprocess according to claim 23, characterized in that the herbicideinhibiting EPSPS is glyphosate.
 35. The process according to claim 32,characterized in that the herbicide is ioxynil.
 36. The processaccording to claim 22, wherein the second coding sequence encodestolerance to glyphosate.
 37. The process according to claim 22, whereinthe second coding sequence encodes an EPSPS conferring tolerance toglyphosate.
 38. The process according to claim 22, wherein the secondcoding sequence encodes glyphosate oxidoreductase.
 39. The processaccording to claim 22, wherein the second coding sequence encodestolerance to phosphinothricin.
 40. The process according to claim 22wherein said second coding sequence encodes tolerance to a herbicidefrom the dihalohydroxybenzonitrile family.
 41. The process according toclaim 40 wherein said herbicide is bromoxynil.
 42. The process accordingto claim 40, wherein said herbicide is ioxynil.
 43. A process forproducing transgenic plants with multiple herbicide tolerance comprisingcrossing a transgenic plant comprising at least one basic genecomprising a coding sequence encoding a mutated HPPD with anothertransgenic plant comprising at least a second basic gene comprising asecond coding sequence encoding an enzyme conferring on plants toleranceto a herbicide, in order to obtain plants with multiple tolerance tofield application rates of these herbicides.